From: Peter Zijlstra <peterz@infradead.org>
To: Elizabeth Figura <zfigura@codeweavers.com>
Cc: "Arnd Bergmann" <arnd@arndb.de>,
"Greg Kroah-Hartman" <gregkh@linuxfoundation.org>,
"Jonathan Corbet" <corbet@lwn.net>,
"Shuah Khan" <shuah@kernel.org>,
linux-kernel@vger.kernel.org, linux-api@vger.kernel.org,
wine-devel@winehq.org, "André Almeida" <andrealmeid@igalia.com>,
"Wolfram Sang" <wsa@kernel.org>,
"Arkadiusz Hiler" <ahiler@codeweavers.com>,
"Andy Lutomirski" <luto@kernel.org>,
linux-doc@vger.kernel.org, linux-kselftest@vger.kernel.org,
"Randy Dunlap" <rdunlap@infradead.org>,
"Ingo Molnar" <mingo@redhat.com>, "Will Deacon" <will@kernel.org>,
"Waiman Long" <longman@redhat.com>,
"Boqun Feng" <boqun.feng@gmail.com>
Subject: Re: [PATCH v4 02/27] ntsync: Introduce NTSYNC_IOC_WAIT_ALL.
Date: Wed, 17 Apr 2024 13:37:03 +0200 [thread overview]
Message-ID: <20240417113703.GL30852@noisy.programming.kicks-ass.net> (raw)
In-Reply-To: <20240416010837.333694-3-zfigura@codeweavers.com>
On Mon, Apr 15, 2024 at 08:08:12PM -0500, Elizabeth Figura wrote:
> + if (atomic_read(&sem->all_hint) > 0) {
> + spin_lock(&dev->wait_all_lock);
> + spin_lock_nest_lock(&sem->lock, &dev->wait_all_lock);
>
> + prev_count = sem->u.sem.count;
> + ret = post_sem_state(sem, args);
> + if (!ret) {
> + try_wake_all_obj(dev, sem);
> + try_wake_any_sem(sem);
> + }
>
> + spin_unlock(&sem->lock);
> + spin_unlock(&dev->wait_all_lock);
> + } else {
> + spin_lock(&sem->lock);
> +
> + prev_count = sem->u.sem.count;
> + ret = post_sem_state(sem, args);
> + if (!ret)
> + try_wake_any_sem(sem);
> +
> + spin_unlock(&sem->lock);
> + }
>
> if (!ret && put_user(prev_count, user_args))
> ret = -EFAULT;
vs.
> + /* queue ourselves */
> +
> + spin_lock(&dev->wait_all_lock);
> +
> + for (i = 0; i < args.count; i++) {
> + struct ntsync_q_entry *entry = &q->entries[i];
> + struct ntsync_obj *obj = entry->obj;
> +
> + atomic_inc(&obj->all_hint);
> +
> + /*
> + * obj->all_waiters is protected by dev->wait_all_lock rather
> + * than obj->lock, so there is no need to acquire obj->lock
> + * here.
> + */
> + list_add_tail(&entry->node, &obj->all_waiters);
> + }
This looks racy, consider:
atomic_read(all_hints) /* 0 */
spin_lock(wait_all_lock)
atomic_inc(all_hint) /* 1 */
list_add_tail()
spin_lock(sem->lock)
/* try_wake_all_obj() missing */
I've not yet thought about if this is harmful or not, but if not, it
definitely needs a comment.
Anyway, I need a break, maybe more this evening.
next prev parent reply other threads:[~2024-04-17 11:37 UTC|newest]
Thread overview: 55+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-04-16 1:08 [PATCH v4 00/30] NT synchronization primitive driver Elizabeth Figura
2024-04-16 1:08 ` [PATCH v4 01/27] ntsync: Introduce NTSYNC_IOC_WAIT_ANY Elizabeth Figura
2024-04-16 1:08 ` [PATCH v4 02/27] ntsync: Introduce NTSYNC_IOC_WAIT_ALL Elizabeth Figura
2024-04-17 11:37 ` Peter Zijlstra [this message]
2024-04-17 20:03 ` Elizabeth Figura
2024-04-18 9:35 ` Peter Zijlstra
2024-04-19 16:28 ` Peter Zijlstra
2024-05-14 4:15 ` Elizabeth Figura
2024-04-16 1:08 ` [PATCH v4 03/27] ntsync: Introduce NTSYNC_IOC_CREATE_MUTEX Elizabeth Figura
2024-04-16 1:08 ` [PATCH v4 04/27] ntsync: Introduce NTSYNC_IOC_MUTEX_UNLOCK Elizabeth Figura
2024-04-16 1:08 ` [PATCH v4 05/27] ntsync: Introduce NTSYNC_IOC_MUTEX_KILL Elizabeth Figura
2024-04-16 1:08 ` [PATCH v4 06/27] ntsync: Introduce NTSYNC_IOC_CREATE_EVENT Elizabeth Figura
2024-04-16 1:08 ` [PATCH v4 07/27] ntsync: Introduce NTSYNC_IOC_EVENT_SET Elizabeth Figura
2024-04-16 1:08 ` [PATCH v4 08/27] ntsync: Introduce NTSYNC_IOC_EVENT_RESET Elizabeth Figura
2024-04-16 1:08 ` [PATCH v4 09/27] ntsync: Introduce NTSYNC_IOC_EVENT_PULSE Elizabeth Figura
2024-04-16 1:08 ` [PATCH v4 10/27] ntsync: Introduce NTSYNC_IOC_SEM_READ Elizabeth Figura
2024-04-16 1:08 ` [PATCH v4 11/27] ntsync: Introduce NTSYNC_IOC_MUTEX_READ Elizabeth Figura
2024-04-16 1:08 ` [PATCH v4 12/27] ntsync: Introduce NTSYNC_IOC_EVENT_READ Elizabeth Figura
2024-04-16 1:08 ` [PATCH v4 13/27] ntsync: Introduce alertable waits Elizabeth Figura
2024-04-16 1:08 ` [PATCH v4 14/27] selftests: ntsync: Add some tests for semaphore state Elizabeth Figura
2024-04-16 1:08 ` [PATCH v4 15/27] selftests: ntsync: Add some tests for mutex state Elizabeth Figura
2024-04-16 1:08 ` [PATCH v4 16/27] selftests: ntsync: Add some tests for NTSYNC_IOC_WAIT_ANY Elizabeth Figura
2024-04-16 1:08 ` [PATCH v4 17/27] selftests: ntsync: Add some tests for NTSYNC_IOC_WAIT_ALL Elizabeth Figura
2024-04-16 1:08 ` [PATCH v4 18/27] selftests: ntsync: Add some tests for wakeup signaling with WINESYNC_IOC_WAIT_ANY Elizabeth Figura
2024-04-16 1:08 ` [PATCH v4 19/27] selftests: ntsync: Add some tests for wakeup signaling with WINESYNC_IOC_WAIT_ALL Elizabeth Figura
2024-04-16 1:08 ` [PATCH v4 20/27] selftests: ntsync: Add some tests for manual-reset event state Elizabeth Figura
2024-04-16 1:08 ` [PATCH v4 21/27] selftests: ntsync: Add some tests for auto-reset " Elizabeth Figura
2024-04-16 1:08 ` [PATCH v4 22/27] selftests: ntsync: Add some tests for wakeup signaling with events Elizabeth Figura
2024-04-16 1:08 ` [PATCH v4 23/27] selftests: ntsync: Add tests for alertable waits Elizabeth Figura
2024-04-16 1:08 ` [PATCH v4 24/27] selftests: ntsync: Add some tests for wakeup signaling via alerts Elizabeth Figura
2024-04-16 1:08 ` [PATCH v4 25/27] selftests: ntsync: Add a stress test for contended waits Elizabeth Figura
2024-04-16 1:08 ` [PATCH v4 26/27] maintainers: Add an entry for ntsync Elizabeth Figura
2024-04-16 1:08 ` [PATCH v4 27/27] docs: ntsync: Add documentation for the ntsync uAPI Elizabeth Figura
2024-04-16 2:13 ` Randy Dunlap
2024-04-16 8:14 ` [PATCH v4 00/30] NT synchronization primitive driver Peter Zijlstra
2024-04-16 8:49 ` Greg Kroah-Hartman
2024-04-16 15:50 ` Peter Zijlstra
2024-04-16 15:53 ` Peter Zijlstra
2024-04-16 16:19 ` Peter Zijlstra
2024-04-16 21:18 ` Elizabeth Figura
2024-04-17 5:21 ` Peter Zijlstra
2024-04-16 21:18 ` Elizabeth Figura
2024-04-16 22:18 ` Elizabeth Figura
2024-04-19 16:16 ` Peter Zijlstra
2024-04-19 20:46 ` Elizabeth Figura
2024-05-07 0:40 ` Elizabeth Figura
2024-05-07 0:50 ` Elizabeth Figura
2024-04-17 5:24 ` Peter Zijlstra
2024-04-16 16:05 ` Peter Zijlstra
2024-04-16 21:18 ` Elizabeth Figura
2024-04-17 5:22 ` Peter Zijlstra
2024-04-17 6:05 ` Elizabeth Figura
2024-04-17 10:01 ` Peter Zijlstra
2024-04-17 20:02 ` Elizabeth Figura
2024-05-15 23:32 ` Elizabeth Figura
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